The present invention relates to an oil strainer and more specifically to an air accumulation preventing structure for an oil strainer.
In an automatic transmission for a vehicle, a control valve body including an oil pressure control circuit is disposed in an oil pan covering a lower opening of a transmission case. The oil pan is arranged to recover and store an oil used for lubrication and operation in a transmission mechanism. The oil in the oil pan is sucked through an oil strainer by an oil pump, and used again for the lubrication and operation of the transmission mechanism. The oil to be used for the operation of the transmission mechanism is supplied from the oil pump to the control valve body.
The oil pressure control circuit in the control valve body includes a pressure regulating valve (or regulator valve) for adjusting the discharge or outlet pressure of the oil pump to a predetermined pressure level, a spool valve for changing over connection among oil passages and a pressure regulating valve for controlling the pressure of the oil used for operating the transmission mechanism. The oil supplied from the oil pump to the control valve body is passed through the oil pressure control circuit for the pressure adjustment, and thereafter used for the operation which is engagement of friction engagement elements in the case of a step automatic transmission such as a transmission using a planetary gear system, and which is variation of a pulley width in the case of a continuously variable belt-type automatic transmission, for example.
The control valve body is provided with a discharge hole for the oil (drain oil) discharged from a pressure regulating valve. Ordinarily, the oil is discharged through this discharge hole into the oil pan.
A patent document 1 (JP 0415354A) shows an automatic transmission in which the discharge hole is formed in an oil strainer, and the oil discharged from the pressure regulating valve is discharged directly into the oil strainer.